Potassium toxicity would be a problem long before the radiation. You'd need to eat 400 bananas a day to eventually die from it which would be at most a ~50 microSievert/day exposure. Occupational exposure limits are in the range of 50 milliSieverts in one year or 100 mS cumulative total over five years. Four thousand bananas in one day would probably kill an adult due to potassium but only expose them to ~20 mS if they ate 4k bananas a day for a year.
> High, acute potassium intakes have been associated with symptoms related to neuromuscular dysfunction, including weakness, paralysis, nausea, vomiting, and diarrhea. These symptoms, however, do not consistently develop prior to life-threatening cardiac arrhythmias.
That said, radioactive isotopes that make it into the digestive tract are far more dangerous than external exposure (and then again, the potassium isotopes aren't accumulated so it might be a wash)
> High, acute potassium intakes have been associated with symptoms related to neuromuscular dysfunction, including weakness, paralysis, nausea, vomiting, and diarrhea. These symptoms, however, do not consistently develop prior to life-threatening cardiac arrhythmias.
https://www.ncbi.nlm.nih.gov/books/NBK545424/
That said, radioactive isotopes that make it into the digestive tract are far more dangerous than external exposure (and then again, the potassium isotopes aren't accumulated so it might be a wash)